Are you out there Novak?? Motor Spoecifications

[Rocksalt]

Dear Novak,

I notice that you aren't posting specifications of your motors. I would like to know the RPM/Volt of the 'R' series motors as well as the current drawn. A torque/HP curve would be great!

I don't know if you have omitted this imformation to keep the competition down or what the reason might be. Could this information be available to the public?

Thanks,

Novak User #8675309 :)

For those that have a dyno, please dyno the 4.5R. Inquring minds want to know.

[Jev]

Bob Novak has aready said that he has not posted these figures because he beleives they can by misleading and not always comparable. I personaly would love to see all the car suitable motors compared on a dyno side by side. As well as a torque curve, a measure of throttle responce would be pretty cool too.

[ElectricThunder]

They don't post performance numbers because each company has a different way of dynoing or rating their motors. For example; Lehner's load for their motors may be different than what Novak uses, or they may use different machines.

Anyways, Optima man kinda figured out (or guesstimated) the Kvs of the 6.5 and 5.5. I think he said they were:

6.5= about 5000kv-5500
5.5= about 6500kv-7000

Those should be at least ball park numbers (very rough estimates).

If you're trying to decide what motor is good for what application, Novak has, on their site, what each motor is reccommended for (IE- the 4.5 is reccommended for TC usage, while the 6.5 can be used for STs)

[Rocksalt]

They don't post performance numbers because each company has a different way of dynoing or rating their motors. For example; Lehner's load for their motors may be different than what Novak uses, or they may use different machines.

Anyways, Optima man kinda figured out (or guesstimated) the Kvs of the 6.5 and 5.5. I think he said they were:

6.5= about 5000kv-5500
5.5= about 6500kv-7000

Those should be at least ball park numbers (very rough estimates).

If you're trying to decide what motor is good for what application, Novak has, on their site, what each motor is reccommended for (IE- the 4.5 is reccommended for TC usage, while the 6.5 can be used for STs)


What is the "kv" rating? is it kvA, kvW, what is that reference in comparison to amps or watts?

[Rocksalt]

OK, your referring to the rev's pr. volt. How would I calculate the amps for any given motor?

[kschauwe]

Amps are largely determined by load. And unloaded motor will draw far less than a motor in a truck/car.

[tcolesen]

kschauwe is right. It would be pretty close to impossible to determine the amp draw of a BL motor. The load depends on so many things, like gearing, tire size, aerodynamics, acceleration, battery voltage, etc. The closest you can get is by using a device that goes inbetween the battery and the speed control that gives the amp draw and battery voltage.

[WJ Birmingham]

Per the Eagle Tree Data logger we have here in the shop, with a 3800 Li-Mn Apogee pack and a 4.5R Novak in our TC4 FT (on Ozite), we're seeing spikes up to 60A, with norms in the 45-50A range.

-WJ
www.ApogeePacks.com

[TimisTim]

So I know ohms law says that if you double the voltage then your half the amps right?

I used a 2S 6000 lipo good for 60amp constant and 72 burst on a Feigao 7L motor. It did fine under those conditions, so if I hook two of those packs together in series (4S) would the motor pull more amps in the given application?

I think the answer is yes......

[Rocksalt]

It would pull half the amps IF the load was the same as well as the speed. ANother words... if you pull less than 1/2 throttle all will be the same. Go past and you are gonna reach new speeds and new currents.

[SpEEdyBL]

No, it will pull twice the amps. Ohms law. Amps = Volts/Resistance.

[topelement]

No, it will pull twice the amps. Ohms law. Amps = Volts/Resistance.

Do you know about electronics? Doubling the voltage will reduce the amp draw. It's the same reason you can use thinner wires when using more cells.

[Rocksalt]

Do you know about electronics? Doubling the voltage will reduce the amp draw. It's the same reason you can use thinner wires when using more cells.

uhmm... do you, lol.

If you double the voltage the current will be what it was before at 1/2 throttle. Voltage is pressure. More pressure available means more current.

Do a few Ohms law calculations and you will see that current is proportional to voltage. What happens when the batteries run down, are you increasing current?

[Jev]

No point get mad with each other about this :p

This is what ohms law has in relation to this.

if watts is equal to power

the same amount of watts can be achieved with either 2 to 1 amps to volts ratio, or visa versa.

But electric motors work more effeciantly with a higher number of winds, and this can only be achieved with higher voltage+low amps as aposed to the other way around.

when the batteries run down the amps stay the same but the voltage drops. But as the voltage drops so does the rpm of the motor and in turn so does the amps ;).

[topelement]

uhmm... do you, lol.

If you double the voltage the current will be what it was before at 1/2 throttle. Voltage is pressure. More pressure available means more current.

Do a few Ohms law calculations and you will see that current is proportional to voltage. What happens when the batteries run down, are you increasing current?


???
Why do you think auto makers are switching to 42 volt systems? Since new cars have so many electronics, the 12v wire harnesses are getting larger and heavier. Running at 42v, they can use thinner wires since the electronics will be pulling less amps.

[Rocksalt]

I=E/R
I=7.4V/5
I=1.48
Watts=10.952
1.99 Horsepower


I=E/R
I=14.8/5
I=2.96
Watts=43.808
1.99 Horsepower

some tidbits to read
http://en.wikipedia.org/wiki/Induction_motor

[kschauwe]

If you increase the voltage without changing the motor windings, the current will increase also. To run double the voltage, half the current, you need to increase the motor windings (higher resistance).
btw 746 watts = 1 horsepower input.

[kurrz]

???
Why do you think auto makers are switching to 42 volt systems? Since new cars have so many electronics, the 12v wire harnesses are getting larger and heavier. Running at 42v, they can use thinner wires since the electronics will be pulling less amps.
This is a valid point but, this does'nt hold true with dc motors.

[Jev]

If you increase the voltage without changing the motor windings, the current will increase also. To run double the voltage, half the current, you need to increase the motor windings (higher resistance).
btw 746 watts = 1 horsepower input.

I think you will find that the current will actualy go down. Because the motor will not be able to find as much load with the extra power from the higher voltage. Either the wheel will spin or you will be going faster which means the motor does not draw as many amps(faster rpm=less amps).

[enricopalazzo]

5.5R
20 amp load 4.8V (4 cell)
30100 RPM
30 amp load 4.8V (4 cell)
28060 RPM
20 amp load 7.2V (6 cell)
45180 RPM
30 amp load 7.2V (6 cell)
42091 RPM
6.5R
20 amp load 4.8V (4 cell)
24180 RPM
30 amp load 4.8V (4 cell)
22380 RPM
20 amp load 7.2V (6 cell)
36280 RPM
30 amp load 7.2V (6 cell)
33580 RPM

[Flyojumper]

Thanks for the numbers enricopalazzo! Do you happen to have the 4.5R or 7.5R numbers too?
Does anyone know why the 6.5R seems to be right about exactly equal to the ss5800 in Kv even though it's a 6.5 turns versus an 8.5t? Are they about equivalent in speed and torque?

[enricopalazzo]

Sorry, thats all i could get out of charlie :) He wont tell me anythin about the 4.5r which is what i want to know the most.

[Rocksalt]

Thank You enricopalazzo. I will test mine when I get it back and post the results between the 2.